During the temperate months of the year many pest populations in various areas of the U.S. reach levels causing severe problems. One pest, the mosquito, can be distracting, can cause bites which itch, and in certain areas can be a vector for the spread of communicable disease such as equine encephalitis. Mosquito populations vary during temperate periods of the year, depending on rainfall, temperature, and other conditions. While the lifespan of an adult mosquito is not long, mosquito larvae can continually mature throughout the year into the adult stage, resulting in the continuing resupply of the mosquito population. Many communities have combatted mosquito populations by fogging or spraying the environment with an insecticide, adding insecticide to likely hatching sites, and by distributing a variety of slow release insecticide compositions into the environment.
The treatment of large areas of the environment having significant numbers of trees, shrubs, and other vegetation requires a particular form of pest control agent to effectively control populations. A pest control agent in the form of dense granules is preferred in aerial applications. Such dense granules permit applications of pest control agents in winds up to 14 miles per hour as these granules can penetrate dense vegetation canopies present during the summer months. Dense granular pest control means can remain effective for extended periods of time when applied to field sites in advance of breeding. During the breeding season dense granules can regulate the rate of pesticide release over an extended period of time.
In one embodiment, the pest control means can be applied to a site, can be activated by flooding, and while wet, release significant proportions of the pesticide.
Many other pests can cause severe problems during their growth or reproductive cycles. Such cycles generally correspond to the temperate seasons of the year. Mollusks in both the adult and larval forms can infest fresh water, damage flora and fauna, provide a disease vector, and pose cosmetic problems. Fungi and algae grow rapidly in fresh water and can make water unpleasant for recreational purposes, may produce toxins which poison farm animals and may make water unfit for human consumption. A variety of plants can grow in unwanted areas, reducing crop yields and presenting weed control problems in many residential and agricultural environments.
Many attempts have been made to combat these pest control problems using a variety of pesticides. Pesticides have been encapsulated with both macro and micro-encapsulation processes, in ceramic materials, biodegradable polymers, porous mineral supports, cellulosic derivatives, polyurea compounds, gypsum and other supports in order to protect the insecticide from the environment and to ensure a controlled release, attempting substantial control of pest populations. An effective pest control concentration is defined as a concentration effective to kill a substantial fraction of at least one form or stage of the pest during its life cycle, or a concentration effective to prevent development or maturation of a form or stage of the pest during its life cycle. The pesticide should be released by the pest control means at an even rate such that significant amounts are not wasted. Pesticides should be protected from the effects of atmospheric oxidation, electromagnetic radiation (light energy or ultraviolet radiation), or other factors, which cause the chemical decomposition of the pesticide. In areas of dense vegetation the pest control means can be of small size, 0.5 to 4.0 mm in diameter, to permit even distribution and penetration of such dense vegetation in environmental areas where pest control applications are needed, and of a distribution density which is at least about 5.5.times.10.sup.-5 gm/cm.sup.2 to provide for adequate distribution over the desired areas when applied by fixed wing and rotocraft. The pesticide composition and means should comprise natural materials, be biodegradable, and be of low cost.
Accordingly, a substantial need exists for a controlled release granule pest control composition that can be made into a granular pest control means and can be applied by aircraft or by hand. A further need exists for a pest control means that can provide substantial control of pest populations for a period of 10-30 days, which protects the pesticide from substantial degradation, effectively penetrate dense vegetation, provide multiple and uniform placement of controlling particles throughout the treated environment, and provide a controlled, continuous rate of release that maintains an effective pest controlling concentration of pesticide in the environment.